In a conventional temperature-controlled vessel, a temperature-adjusted gas medium is circulated in the vessel to set an apparatus in the vessel at the same temperature as that of the gas medium, so that the vessel serves as a temperature-controlled vessel. A prior art for an exposure apparatus that utilizes a temperature-controlled vessel will be described (see, e.g., Japanese Patent Laid-Open No. 10-154655). FIG. 9 is a schematic sectional view showing a temperature-controlled vessel in an exposure apparatus EO. The exposure apparatus EO has an exposure unit 114 having an illumination optical system, projection lens system, reticle stage, wafer stage, and the like (neither is shown) in a chamber 101a formed of a housing 101, a reticle library 113 disposed near the exposure unit 114, a carrier table 111 for placing a wafer carrier 112 thereon, and the like.
In one side wall of the housing 101, a reticle inlet/outlet port 109 provided with an opening/closing door 109a is formed at a portion corresponding to the reticle library 113, and a wafer inlet/outlet port 110 provided with an opening/closing door 110a is formed at a portion corresponding to the carrier table 111.
A ceiling space 102 partitioned by a filter 102a, through which clean air blows out as a down flow, is formed in the upper portion in FIG. 9 of the chamber 101a. An under-floor space 104 partitioned by a floor 103 having a plurality of exhaust ports is formed in the lower portion in FIG. 9 of the chamber 101a. The ceiling space 102 and under-floor space 104 communicate with each other through a circulation duct 105 in which a temperature adjustment unit 106 is interposed. Air introduced by an air introduction fan 107 to the ceiling space 102 blows out as a down flow of clean air through the filter 102a. Air collected in the under-floor space 104 by an exhaust fan 108 is adjusted to a predetermined temperature by the temperature adjustment unit 106 of the circulation duct 105, is supplied to the ceiling space 102 by a circulation fan 109, and is circulated again.
The temperature-adjusted air is circulated in the chamber in this manner, so that the temperature of the exposure unit 114 sensitive to a temperature change is maintained at a constant value.
In the prior art example, the temperatures of the devices in the vessel are adjusted through the gas. In an apparatus with a vessel the interior of which is to be evacuated, the temperature in the apparatus cannot be adjusted through gas. In particular, in an exposure apparatus which exposes a target object such as a single-crystal substrate for a semiconductor wafer, a glass substrate for a liquid crystal display (LCD), and the like by utilizing EUV (extreme ultraviolet) light, the optical system must be maintained in a vacuum atmosphere in order to prevent the EUV light from attenuating by absorption by air.
When the gas as a heating medium does not exist, heat flow is limited to radiation and heat conduction through members that connect the devices and a vessel that accommodates the devices. Generally, when installing a precision device, the device is often fixed by 3-point support so that no looseness is produced or that the device will not be adversely affected by relative deformation between the device and vessel. For this reason, the contact area between the device and vessel is very small, and heat flow by conduction is small. Even if temperature adjustment by heat conduction is possible, only some device in the vessel can be temperature-adjusted, and it is difficult to maintain the whole devices at a uniform temperature.
From the foregoing, in a vessel such as a vacuum temperature-controlled vessel that forms a pressure-reduced atmosphere, radiation is significant as a means for maintaining devices or the like in the vessel at a constant value. Assume an arrangement in which, as shown in FIG. 8, the temperature of whole members that constitute a vessel 7 is adjusted to a constant, uniform value, so that a device in the vessel 7 is equilibrated with the temperature of the vessel members by radiation as heat flow. In FIG. 8, reference numeral 1 denotes a target to be temperature-adjusted (in this case, a substrate as an exposure target); 2, a top plate; 3, guides; 4, driving sections; 5, a stage surface plate; 6, refrigerant pipes; 7, a vacuum vessel; 8, an optical system device; 9, heat-insulating support members; 10, refrigerant pipes (for radiation shielding plates); and 12, an exhaust device.
When the temperature-controlled vessel is used as a vacuum vessel, the exhaust device 12 for maintaining the vacuum is connected to the vessel 7. If the exhaust device 12 is constituted by a turbo-molecular pump or the like, heat is generated in a large amount, and the exhaust device 12 is generally connected directly to the vessel 7. In an EB (Electron Beam) exposure apparatus or the like, a large amount of heat generated by an electron gun is known. Due to these influences of heat generation, a nonuniform temperature distribution tends to be formed in the vessel 7. Regarding the vacuum vessel, the thickness of the vessel 7 is generally large in order to increase the resistance against the pressure, and accordingly the heat capacity is large. It is relatively easy to keep the temperature constant in the vessel 7. It is, however, difficult to suppress temperature nonuniformity caused by the heat generation at high accuracy. Depending on the location where the vacuum vessel is installed, the vessel tends to be cooled insufficiently against a large temperature change of the atmosphere of the installation environment. Then, temperature nonuniformity may occur in the vessel and the interior of the vessel.
Generally, a precision device is sensitive to a temperature change. For example, in an exposure apparatus, a substrate as an exposure target and its periphery are allowed to have temperature changes during exposure of only as low as 0.1 m° C. to 1 m° C. Any temperature change exceeding this range may cause resolution nonuniformity. For this reason, demands have been arisen for a vessel that can maintain a device arranged in the vessel at a uniform, constant temperature regardless of the environment where the vessel is installed.